1. Field of the Invention
The present invention relates to an apparatus for controlling the rotation of a motor in a video disc player, a digital audio disc player or the like and, more particularly, to an apparatus adapted for use in reproduction of a rotary recording medium such as a video disc or digital audio disc where information is recorded substantially at a fixed linear density.
2. Description of the Prior Art:
As an apparatus employed for controlling the rotation of a disc driving motor in the conventional video disc player or digital audio disc player, there is known an example disclosed in U.S. Pat. No. 4,223,349 wherein a reproduced synchronizing signal is separated from the information (reproduced composite signal) obtained from the disc and is phase-compared with a reference synchronizing signal, and the rotation of the motor is controlled in accordance with the result of such comparison.
The term "synchronizing signal" in this specification corresponds to a horizontal synchronizing signal, a vertical synchronizing signal and so forth in a video disc player, or to a clock signal and so forth in a digital audio disc player. This definition applies to the following description as well.
However, in such motor rotation control apparatus mentioned, there are some problems including that, when any dropout of the information is existent on the disc surface or the reproduction spot is positioned in a non-recorded portion (generally termed "mirror surface"), it becomes impossible to obtain a stable reproduced synchronizing signal to consequently bring about great variation in the motor rotation rate or runaway of the motor.